Stabilized 2,3-dichloro-1,3-butadiene

ABSTRACT

This invention relates to the stabilization of monomeric 2,3dichloro-1,3-butadiene, wherein a piperazine derivative corresponding to the formula:   IN WHICH R represents hydrogen, a linear of branched alkyl radical with one to five carbon atoms or a linear or branched hydroxyalkyl radical with two to five carbon atoms, is added to the monomer.

United States Patent [1 1 Mayer-Mader et al.

[ STABILIZED 2,3-DlCHLORO-1,3-BUTADIENE [75] Inventors: Rudolf Mayer-Mader, Cologne; Karl Dinges, Odenthal, both of Germany [73] Assignee: Bayer Aktiengesellschaft,

Leverkusen, Germany [22] Filed: Mar. 4, 1971 [21] Appl. No.: 121,180

[30] Foreign Application Priority Data Mar. 25, 1970 Germany P 20 14 382.2

[52] U.S. Cl. 260/6525 P [51] Int. Cl CO7c 17/40, CO7c 17/42 [58] Field of Search 260/6525 R, 652.5 P

[56] References Cited UNITED STATES PATENTS 1,965,369 7/1934 Carothers et a1 260/6525 P 3,082,262 3/1963 Scott 260/6525 P 2,111,253 3/1938 Stoesser et a1. 260/6525 R June 26, 1973 Primary Examiner-Howard T. Mars AttorneyConnolly & Hutz [57] ABSTRACT This invention relates to the stabilization of monomeric 2,3-dichloro-1,3-butadiene, wherein a piperazine derivative corresponding to the formula l ll in which R represents hydrogen, a linear of branched alkyl radical with one to five carbon atoms or a linear or branched hydroxyalkyl radical with two to five carbon atoms, is added to the monomer.

4 Claims, No Drawings STABILIZED 2,3-DICHLORO-1,3-BUTADIENE This invention relates to the stabilization of 2,3- dichloro-l,3-butadiene with piperazine derivatives.

The monomeric 2,3-dichloro-1,3-butadiene obtainable by known methods (for example G.J.Berchet and W.H.Carothers, J.Am. Chem.Soc. 55, 2,004 to 2,007 (1933) shows a very noticeable tendency towards polymerization and is completely polymerized over a period of 24 hours, for example, at room temperature in the presence of air and light (U.S. Pat. specification No. 1,965,369, page 3, lines 19 to 26). Accordingly, considerable difficulties are involved in storing 2,3- dichloro-1,3-butadiene because the monomer can only be prevented from undergoing bulk polymerization at extremely low temperatures. At room temperature, however, it is not long before the formation of polymer product begins, the polymer obtained being completely insoluble in the monomer at room temperature (G.J.Berchet and W.H.Carothers, J.Am.Chem.Soc. 55 (1931), page 2,006, lines 24 to 31).

In order to reduce its tendency towards polymerization, it has been proposed to add to the 2,3-dichloro- 1,3-butadiene inhibitors such as, for example, antioxidants, e.g. hydroquinone, pyrocatechol, tert.-butyl pyrocatechol, pyrogallol, phenyl B -naphthylamine or phenothiazine (cf. for example U.S. Pat. specification No. 1,965,369, page 3, lines 34 to 39). Unfortunately, substances of this kind are unable permanently to inhibit the polymerization of dichlorobutadiene. In addition, it is advisable to store material which has been stabilized in this way at low temperatures in the absence of light and in air-free containers (U.S. Pat. specification No. 1,965,369, page 3, lines 41 to 48). The compounds added as inhibitors have the further disadvantage that, during polymerization of the dichlorobutadiene, they remain to some extent in the polymer follow ing conversion of the monomer. Further, the presence of conventional inhibitors has an adverse effect in cases where the polymer obtained is subjected to further chemical reactions carried out in the presence of radical formers, such as for example bromination as proposed for example in U.S. Pat. specification No. 2,625,373. For example, the addition of bromine to the double bonds is predominantly obtained instead of the required substitution in the allyl position to the double bond (cf. U.S. Pat. specification No. 2,725,373, column 1, lines 65 to 68), in the bromination of 2,3- dichloro-l,3-butadiene'stabilized in the usual way, because the stabilizers present act as radical acceptors, thus partly suppressing the allyl bromination taking place through a radical chain mechanism.

It has now been found that monomeric 2,3-dichlorol,3-butadiene can be effectively stabilized by adding to the monomer a piperazine derivative of the general formula (l):

in which R represents hydrogen, a linear or branched alkyl radical with one to five carbon atoms or a linear dimethylpropyl, 2,2-dimethylpropyl and 3,3- dimethylpropyl.

The following radicals are mentioned as examples of hydroxyalkyl radicals containing two to five carbon atoms: l-hydroxyethyl, 2-hydroxyethyl, l-hydroxypropyl, 2-

hydroxypropyl, 3-hydroxypropyl, lhydroxymethylethyl, l-hydroxy-l-methylethyl, lhydroxybutyl, 2-hydroxybutyl, S-hydroxybutyl, 4'

hydroxybutyl, 1,l-dimethyl-2-hydroxyethyl, l-hydroxymethylpropyl, l-methyl-l-hydroxypropyl, 1-methyl-2- hydroxypropyl, l-methyl-3-hydroxypropyl, l-hydroxy- 2-methylpropyl, 2-methyl-2-hydroxypropyl, 2-hydroxymethylpropyl, 2-methyl-3-hydroxypropyl, lhydroxypentyl, 2-hydroxypentyl, 3-hydroxypentyl, 4- hydroxypentyl, S-hydroxypentyl, l-methyll hydroxybutyl, 1 -methyl- 1 -hydroxybutyl, 1-methyl-3- hydroxybutyl, l-methyl-4-hydroxybutyl, l-hydroxy-2- methylbutyl, 2-methyl-2-hydroxybutyl, 2-hydroxymethylbutyl, 2-methyl-3-hydroxybutyl, 2-methyl-4- hydroxybutyl, l-hydroxy-3-methylbutyl, 2-hydroxy-3- methylbutyl, 3-hydroxymethylbutyl, 3-methyl-5- hydroxybutyl, 3 -methyl-4-hydroxybutyl, lhydroxymethyl- 1 -methylpropyl, 1,1-dimethyl-2- hydroxypropyl, 1 ,1-dimethyl-3-hydroxypropyl, 1-hydroxy-2-methylpropyl, 1-hydroxy-2-methylpropyl, 1-methyl-2-hydroxymethylpropyl, 1,2-dimethyl-2- hydroxypropyl, 1-hydroxy-2,3-methylpropyl, 2 -hydroxymethyl-2-methylpropyl, 3-hydroxymethylbutyl, 3-hydroxy-3-methylbutyl, 2*hydroxy-3- methylbutyl, l-hydroxymethylbutyl and 1-hydroxy-2,2- dimethylpropyl.

The following piperazines are mentioned as examples of stabilizers for the monomeric- 2,3-dichloro-1,3- butadiene corresponding to the general formula (I):- piperazine, N-methylpiperazine, N-ethylpiperazine, N-propylpiperazine, N-isopropylpiperazine, N-butylpiperazine, N-tert.-butylpiperazine, N-(methylpropyl)- piperazine, N-(Z-methylpropyl)-piperazine, N-( pentyl)-piperazine, N-(1-methylbutyl)-piperazine, N-(2-methylbutyl)-piperazine, N-(3-methylbutyl)- piperazine, N-(1,1,-dimethylpropyl)-piperazine, N- (1 ,2-dimethylpropyl)-piperazine, N-(2,2- dimethylpropyl)-piperazlne, N-(3,3-dimethylpropyl)- piperazine, N-(1-hydroxyethyl)-piperazine. N-(2- hydroxyethyl)-piperazine, N-( l-hydroxypropyl)- piperazine N-(Z-hydroxypropyl)-piperazine, N-(3- hydroxypropyl)piperazine, N-(1-hydroxymethylethyl)- piperazine, N-(l-hydroxy-l-methyl-ethyl)-piperazine, N-(l-hydroxybutyl)-piperazine, N-(2-hydroxybutyl)- piperazine, N-(3-hydroxybutyl)-piperazine, N-(4- hydroxybutyl)-piperazine, N-( 1,l-dimethyl-2- hydroxyethyl)-piperazine,N-(1-hydroxymethylpropyl)- piperazine, N-(1-methyl-1-hydroxypropyl)-piperazine, N-( 1-methyl2-hydroxypropyl)-piperazine, N-( 1- methyl-3-hydroxypropyl)-piperazine, N-(1-hydroxy-2- methylpropyl)-piperazine, N-(2-methyl-2- hydroxypropyl)-piperazine, N-(2- hydroxymethylpropyl)-piperazine, N-(2-methyl-3- hydroxypropyl)-piperazine, N-( l -hydroxypentyl)- piperazine N4?'hydlioxypemyl)'piperazine IIN NII o1-0000nn L IIN No0uslls hydroxypentyl)-plperazlne, N-(4-hydroxypentyl)- piperazine, N-(-hydroxypentyl)-piperazine, N-lmethyl- 1 -hydroxybutyl)-piperazine, N-( l -methyl-2- l v hydroxybutyU-piperazine, N-(l-methyl-3- 5 m Hydrolysis m hydroxybutyl)-plperazlne, N-( l-methyl-4- CHFN. NH IPCOOWIR hydroxybutyl )-piperazine, N-( l -hydroxy-2- y yU-p l y The hydroxyalkyl piperazines of formula (I) are gen- Y Y yU-P P s y Y Y yU- erally obtained by reacting piperazine with alkylene oxp p y y y y )-P P ides (cfv Kirk-()thmer, Encyclopedia of chem. Technol- N-(2-melhyl-4-hydroxybutyl)-piperazin ogy, second Edition, Vol. 15, John Wiley and Sons, hydroxy-3-methylbutyl)-piperazine, N-(2-hydroxy-3- 1968, page 639, lines 24 to 30). methylbutyl)-piperazine, N-(3-hydroxymethylbutyl)- The compounds which can be used in the process acpiperazine, N-(3-hydroxymethylbutyl)-piperazine, N- cording to the invention can of course also be used in (3 -methyl-3-hydroxybutyl)-piperazine, N-(3-methyl-4- conjunction with other conventional inhibitors. hydroxybutyl)-piperazine, N-( l-hydroxymethyl-l The percentages quoted in the following Example are methylpropyl)-piperazine, N-( 1,1-dimethyl-2- by weight.

hydroxypropyl)-piperazine, N-( 1,1-dimethyl-3- hydroxypropyl)-piperazine, N-(l-hydroxymethyl-Z- 20 EXAMPLE I melhylpropyn'plperazlnei To measure monomer stability at room temperature, p p 'P P F u' y y y polymeric 2,3-dichloro-l,3-butadiene is freed from all y P U-p l s the impurities and additives present in it, especially stay yp pyb-p p y yfibilizers, by distillation in vacuo. 100 g samples of the y pmp hp p i 'a' y y 25 stabilizer-free material obtained are poured into glass y p py )-p p y ybottles. The piperazine derivatives identified in the first.

w ym y 'p p s y y ly yncolumn of Table l are then added in' the concentration P'P V y yy yb-p p specified in column 2 of Table I. N) cc. of stabilized y y y y )-p p y y- 2,3-dichloro-l,3-butadiene are removed from the samy p py )-p p 30 ple bottle at the time intervals indicated in the follow- In g n the process according t the invention is ing columns of Table l, and poured into 100 cc of methcarricd out by adding to the freshly prepared 2,3- anol. Where bulk polymerization has taken place, dichloro-l,3-butadiene from 0.01 to percent, and white insoluble polymer particles are formed (identiprefcrably from 0.1 to 1 percent of the piperazine comfied by the words polymer formation in the correpound of formula (I), based on 100 parts by weight of 35 sponding column of Table l).

V r H Tfififfi v 7 Behaviour of 2,3-diehloro-1,3-butadiene after the following storages periods at room temperature Per- 0 1 2 3 4 5 10 Stabiliser cent day day days days days days days days days days days Phenothiazine (for comparison) N-methyl piperazine 8: Piperazine c N-hydroxyethyl piperazine Polymer formation,

the monomer. The piperazine derivative is best added Table I shows that a shelf life of at least 30. days can directly to the monomeric 2,3-dichlorobutadiene in liqbe obtained in cases where N-methyl piperazine, piperuid form at room temperature and at normal pressure azine and N-hydroxyethyl piperazine are used to stabiin the presence or abence of the usual monomer stabilize 2,3-dichloro-1,3-butadiene, whilst, in the absence lizers such as p-tert.-butyl pyrocatechol, phenothiazine, of stabilizers,-there are signs of polymer formation in etc. the monomeric dichlorobutadiene after only 2 days.

The product stabilized by the process according to h g in cases where p-terL-butyl pyro e hol the invention can be stored for an almost unlimited peand Phenolhialine are used, p lymer f rmation in bulk riod at room t m t ith t any id gf ol is retarded in relation to the zero sample, there are mer formation. Emulsion polymerization of the mono- Signs of p y formation in 188% 6. a so, after the mer thus stabilized is totally unaffected by addition of dichlol'obutadiene has been slil'ed much Shorter P m ili and the polymer obtained is f fr riods in comparison with samples of the kind that have bili been stabilized with compounds of the general formula I The N-substituted 'piperazines used for the process according to the invention can be obtained by known preparative methods, for example, by blocking one ni- EXAMPLE 2 trogen atom of the piperazine ring which chloroformic Since it is of importance so far as the subsequent ap acid ethyl ester and then reacting the second nitrogen plication of polymeric dichlorobutadiene is concerned atom, for example, in accordance with the following to know whether the polymer still contains stabilizer, scheme which illustrates the preparation of N-methyl differently stabilized monomeric 2,3-dichloro-l,3- piperazine: butadiene was polymerized and worked up, and the redance with US. Pat. specification No. 2,725,373: 12.3 g of polydichlorobutadiene are introduced into a three-necked flask containing 150 ml of tetrachloromethane. The flask is then rinsed with nitrogen and the mixture is boiled under reflux while stirring until a clear solutionisformed. Two solutions are then added dropwise, the firsFconsisting of 7.25 g of bromine dissolved in 20 ml of CCl; and the second of 0.56 g of tert.-butyl peroxide in 5 ml of CCl,. The period of time elapsing before hydrogen bromide is evolved (incubation period) is noted in Table [1.

Allyl bromination was seen to begin at different points in time (incubation period before hydrogen bromide is given off), depending upon the type of stabilizer used. The results are set out in Table II.

TABLE I] Stabilizer in the monomer Table II shows that the period of time elapsing before hydrogen bromide is given off (incubation period) in accordance with the following scheme:

is not delayed in cases where the monomer is stabilized with N-hydroxyethyl piperazine and N-methyl piperazine, whilst, in cases where phenothiazine is used as the stabilizer, the evolution of hydrogen bromide only begins after approximately minutes as an indication of allyl bromination.

What we claim is:

l. A stabilized mixture consisting essentially of 2,3- dichloro-l ,3-butadiene and from 0.01 to 10 percent by weight, based on the weight of 2,3-dichloro-l ,3- butadiene, of a compound of the formula:

i" N l R 4. The mixture of claim 1 wherein R is methyl. 

2. The mixture of claim 1 wherein said compound of said formula is present in said mixture in an amount of from 0.1 to 1 percent by weight, based on the weight of 2,3-dichloro-1,3-butadiene.
 3. The mixture of claim 1 wherein R is hydroxyethyl.
 4. The mixture of claim 1 wherein R is methyl. 